Signaling of transmissions with shortened TTI

ABSTRACT

The disclosure relates to signalling of transmissions with shortened TTI. The disclosure further relates to an RBS and a method performed at the RBS of scheduling resources for a wireless communication device. The disclosure still further relates to a wireless communication device and a method performed at the wireless communication device of being granted data transmission or data reception. In a first aspect of the disclosure, a method performed at an RBS is provided for scheduling resources for a wireless communication device including indicating a grant of a resource for the wireless communication device to transmit or receive data based on DCI and a position of the DCI within a data frame of a downlink control channel.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a Continuation Application of U.S. application Ser. No.16/333,158 filed Mar. 13, 2019, now U.S. Pat. No. 10,980,053, which is aSubmission Under 35 U.S.C. § 371 for U.S. National Stage PatentApplication of International Application No.: PCT/SE2017/050924, filedSep. 25, 2017 entitled “SIGNALING OF TRANSMISSIONS WITH SHORTENED TTI,”which claims priority to U.S. Provisional Application No. 62/402,513,filed Sep. 30, 2016, entitled “SIGNALING OF UPLINK TRANSMISSIONS WITHSHORTENED TTI,” the entireties of all of which are incorporated hereinby reference.

TECHNICAL FIELD

The disclosure relates to signalling of transmissions with shortenedtransmission time interval (TTI). The disclosure further relates to aRadio Base Station (RBS) and a method performed at the RBS of schedulingresources for a wireless communication device. The disclosure stillfurther relates to a wireless communication device and a methodperformed at the wireless communication device of being granted datatransmission or data reception.

BACKGROUND

Latency Reduction with Short Subframes

Packet data latency is one of the performance metrics that vendors,operators and also end-users (via speed test applications) regularlymeasure. Latency measurements are done in all phases of a radio accessnetwork system lifetime, when verifying a new software release or systemcomponent, when deploying a system and when the system is in commercialoperation.

Shorter latency than previous generations of 3rd Generation PartnershipProject (3GPP) Radio Access Technologies (RATs) was one performancemetric that guided the design of Long Term Evolution (LTE). LTE is alsonow recognized by the end-users to be a system that provides fasteraccess to internet and lower data latencies than previous generations ofmobile radio technologies.

Packet data latency is important not only for the perceivedresponsiveness of the system; it is also a parameter that indirectlyinfluences the throughput of the system.

The Hypertext Transfer Protocol/Transmission Control Protocol (HTTP/TCP)is the dominating application and transport layer protocol suite used onthe internet today. According to HTTP Archive(http://httparchive.org/trends.php) the typical size of HTTP basedtransactions over the internet are in the range of a few 10's of Kbyteup to 1 Mbyte. In this size range, the TCP slow start period is asignificant part of the total transport period of the packet stream.During TCP slow start the performance is latency limited. Hence,improved latency can rather easily be showed to improve the averagethroughput, for this type of TCP based data transactions.

Radio resource efficiency could be positively impacted by latencyreductions. Lower packet data latency could increase the number oftransmissions possible within a certain delay bound; hence higher BlockError Rate (BLER) targets could be used for the data transmissionsfreeing up radio resources potentially improving the capacity of thesystem.

One area to address when it comes to packet latency reductions is thereduction of transport time of data and control signalling, byaddressing the length of a transmission time interval (TTI). In LTErelease 8, a TTI corresponds to one subframe (SF) of a length of 1millisecond. One such 1 ms TTI is constructed by using 14 OrthogonalFrequency Division Multiple Access (OFDM) or Single Carrier-FrequencyDivision Multiple Access (SC-FDMA) symbols in the case of normal cyclicprefix and 12 OFDM or SC-FDMA symbols in the case of extended cyclicprefix. In LTE release 13, a study item has started during 2015, withthe goal of specifying transmissions with shorter TTIs that are muchshorter than the LTE release 8 TTI.

The shorter TTIs can be decided to have any duration in time andcomprise resources on a number of OFDM or SC-FDMA symbols within a 1 msSF. As one example, the duration of the short TTI may be 0.5 ms, i.e.seven OFDM or SC-FDMA symbols for the case with normal cyclic prefix. Asanother example, the duration of the short TTI may be 2 symbols.

Uplink Scheduling Grants

The existing physical layer downlink control channels, Physical DownlinkControl Channel (PDCCH) and enhanced PDCCH (ePDCCH), are used to carryDownlink Control Information (DCI) such as scheduling decisions andpower control commands. Both PDCCH and ePDCCH are transmitted once per 1ms SF.

There are currently a number of different Downlink Control Information(DCI) formats, see 3GPP TS 36.212, for uplink and downlink resourceassignments. Uplink scheduling grants use either DCI format 0 or DCIformat 4. The latter is added in Release 10 for supporting uplinkspatial multiplexing.

In general, the DCI for an uplink scheduling grant may contain

-   -   Resource allocation information        -   Carrier indicator        -   Resource allocation type        -   Resource block allocation    -   RS and data related information        -   modulation and coding scheme (MCS)        -   New data indicator        -   Cyclic shift of the uplink demodulation reference signals            (DMRS)        -   Precoding information        -   Transmit power control    -   Other information        -   Sounding Reference Signal (SRS) request        -   Channel Status Information (CSI) request        -   Uplink (UL) index (for time division duplex (TDD))        -   DCI format 0/1A indication (only in DCI format 0 and 1A)        -   Padding        -   Cyclic redundancy check (CRC) scrambled with Radio Network            Temporary Identifier (RNTI) of the terminal            Dynamic Switching Between Lengths of Short TTIs

As mentioned, one way to reduce latency is to reduce the TTI, andinstead of assigning resources with a time duration of 1 ms, there isthen a need to assign resources with shorter duration such as a numberof OFDM or SC-FDMA symbols. This implies a need for User Equipment (UE)specific control signaling that enables indication of such shortscheduling assignments.

Furthermore, there is also a need to be able to dynamically switchbetween TTI duration, for example between legacy 1 ms TTIs as well asshorter TTIs, in order to optimize the spectral efficiency (sinceshorter TTIs may incur higher overhead and/or worse demodulationperformance).

Throughout this application, short PDSCH (sPDSCH) and short PUSCH(sPUSCH) are used to denote the downlink and uplink physical sharedchannels with short TTIs, respectively. Similarly, short PDCCH (sPDCCH)is used to denote downlink physical control channels with short TTIs(sTTIs), an sTTI having a shorter duration than a TTI.

In uplink transmissions, one or more SC-FDMA symbols with DMRStransmitted for each short TTI leads to an increased overhead and acorresponding decrease in data rates, when the length of the TTI isreduced.

SUMMARY

The existing way of operation, e.g. frame structure and controlsignaling, are designed for fixed length 1 ms data allocations, whichmay vary only in allocated bandwidth. Specifically, the current DCIsdefine resource allocations within the entire SF. There is no obvioussolution that allows dynamic configuration of the short TTI duration foruplink transmissions.

A new DCI format can be defined to support short TTI configuration byintroducing a time domain split field. However, this new DCI formattedis designed based on using PDCCH, which is transmitted only once persubframe. Therefore, short TTI scheduling decisions can only be made persubframe.

Flexible DMRS for short TTI transmissions in uplink can be enabled byintroducing a separate DMRS grant and data grant for each sPUSCH. Thismethod allows for flexible and fast reconfiguration of sPUSCH, and itenables UE to transmit DMRS without transmitting user data. However,separating DMRS and data grants increases the control signalingoverhead. Moreover, it increases the complexity for handling of cornercases, where different types of grants are not correctly detected by theuser.

To overcome the drawbacks of previous solutions a fast grant is possiblewhich enables flexible configuration of sPUSCH, by indicating thepositions and lengths of both DMRS and data symbols, as well as thelength of the short TTI.

The uplink fast grants allow for flexible configuration of short TTIsfor uplink transmissions, e.g., flexible TTI lengths within a subframeand to adjust TTI lengths for individual UE needs. However, it also addsmore signaling overhead and an advanced hybrid automatic repeat request(HARQ) design. When the signaling overhead and the implementationcomplexity is a concern, a simplified uplink grant should be designedwhile still supporting promising uplink short TTI transmissionfunctionalities, e.g., DMRS multiplexing and dynamic DMRS insertion.

Other signaling methods for uplink short TTI transmissions are possible.The uplink short TTI configurations, e.g., the positions of referencesymbols in the form of DMRSs and data symbols, and the length of eachTTI are fixed for each SF. The short TTI configuration is signaled by aslow grant, which is transmitted on SF basis in downlink, and it ispossibly common for a group of users. An uplink short TTI transmissionis scheduled by a fast grant, which is user specific and transmitted onsymbol basis in downlink. The proposed solution supports uplink shortTTI transmissions with a much lower signaling overhead andimplementation complexity.

One drawback of this signaling method is the limited flexibility for theconfiguration sPUSCH transmission, due to the fact that the short TTI(sTTI) configuration is signaled by a slow grant.

An object of the disclosure is to solve, or at least mitigate, some ofthese problems in the art, and thus to provide an improved methodperformed by an RBS of scheduling resources for a wireless communicationdevice.

This object is attained in a first aspect of the disclosure by a methodperformed at a Radio Base Station (RBS) of scheduling resources for awireless communication device. The method comprises indicating and/orissuing a grant of a resource for the wireless communication device totransmit or receive data based on Downlink Control Information (DCI) anda position of the DCI within a data frame of a downlink control channel.

This object is attained in a second aspect of the disclosure by an RBSconfigured to schedule resources for a wireless communication device,the RBS comprising a processing unit and a memory, the memory containinginstructions executable by the processing unit, whereby the RBS isoperative to indicate and/or issue a grant of a resource for thewireless communication device (103) to transmit or receive data based onDownlink Control Information, DCI, and a position of the DCI within adata frame of a downlink control channel.

This object is attained in a third aspect of the disclosure by a methodperformed at a wireless communication device of being granted datatransmission or data reception. The method comprises receiving a dataframe of a downlink control channel from an RBS, and determining whethera granted resource of transmission or reception of data is issued and/orindicated based on DCI and a position of the DCI within a data frame ofa downlink control channel.

This object is attained in a fourth aspect of the disclosure by awireless communication device configured to determine whether datatransmission or data reception is granted, comprising a processingcircuit and a memory, the memory containing instructions executable bythe processing circuit, whereby the wireless communication device isoperative to receive a data frame of a downlink control channel from anRBS, and determine whether a granted resource of transmission orreception of data is issued and/or indicated based on DCI and a positionof the DCI within the data frame of the downlink control channel.

In one alternative, one or more particular DCI bit fields at aparticular position in the data frame indicates particular informationto be sent in the uplink for the wireless communication device (alsoreferred to herein as a UE). For instance, DCI bit field “00” at DL sTTI0 may indicate a DMRS followed by two symbols of data, while DCI bitfield “01” at DL sTTI 3 indicates one symbol of data followed by a DMRS,and so on.

Further, a DCI transmitted at a particular sTTI in the downlink, grantsa UL transmission at a predetermined number of sTTIs from the particularsTTI at which the DCI was transmitted.

That is, a UL grant transmitted in the form of DCI data at sTTI n in thedownlink schedules an UL transmission at sTTI n+k. For instance, onesubframe may consist of 6 sTTIs in both UL and DL, if the UL schedulingtiming is n+k with k=6, then, an UL grant transmitted at DL sTTI index=0in a subframe schedules an UL transmission at UL sTTI index 0 in thenext subframe.

As can be concluded, the DCI and the position of the DCI within a dataframe of a downlink control channel indicates the DMRS configuration,the data symbol configuration, and the sTTI length of a correspondingdata frame for uplink transmission (or downlink reception) of the UE.

In an embodiment, a new method for signalling transmissions, especiallyfor the transmissions with shortened TTI length, is provided. The uplinktransmission is signalled by an UL DCI, such as a fast DCI, which istransmitted on symbol basis in a DL sTTI. A field in the UL DCI togetherwith the position of the DCI indicate the configuration of the scheduleduplink user data transmission, including the DMRS configuration, thedata configuration, and the sTTI length. Similarly, a field in a fastDCI together with the position of the DCI may be used to indicate theconfiguration of uplink control channel transmission for the HARQ-ACKfeedback for a DL transmission.

The same methodology can be used for signalling downlink short TTItransmissions.

Advantageously, the proposed solution supports uplink short TTItransmissions with a much lower signalling overhead and implementationcomplexity.

Further advantageous is that, the proposed solution enables dynamicconfigurations of uplink sTTI transmissions on a symbol basis. At thesame time, it supports most of sTTI patterns.

The proposed solution further advantageously supports fixed or differentTTI lengths within a subframe, DMRS multiplexing and dynamic DMRSinsertion functionalities, which can reduce the DMRS overhead and thusimprove the resource utilization for uplink short TTI transmissions.

Thus, a new uplink grant approach for dynamic signalling of uplink shortTTI configurations in which the position of the DCI in DL, incombination with a few control information bits constituting the DCI, isused for indicating UL sTTI length, DMRS positions, and data symbolspositions for control and data channels.

In an embodiment, the RBS detects a need of the wireless communicationdevice to perform an uplink transmission or downlink reception.

In an embodiment, the RBS selects time interval for transmitting thedata frame on the downlink control channel to the wireless communicationdevice.

In a further embodiment, the RBS configures one or more bit fields ofthe DCI to indicate to the wireless communication device thattransmission or reception of data is granted.

In yet a further embodiment, the bit fields of the DCI indicate TTIconfiguration for the indicated grant.

In still a further embodiment, the grant is indicated and/or issued ifthe bit fields of the DCI are appropriately configured and the DCI is inan appropriate position within the data frame of the downlink controlchannel, as determined by the RBS.

In another embodiment, the RBS transmits data to, or receives data from,the wireless communication device upon the indication and/or issuing ofa grant.

In an embodiment, the RBS includes in the DCI a Demodulation ReferenceSignal, DMRS.

In still an embodiment, the position of the DCI within a data frame of adownlink control channel is indicated by means of a downlink sTTI index.

In another embodiment, the RBS determines amount of resources granted tothe wireless communication device and timing of transmission orreception of data.

In yet an embodiment, the DCI and the position of the DCI within a dataframe of a downlink control channel indicates the DMRS configuration,the data symbol configuration, and the short TTI length of acorresponding data frame for uplink transmission or downlink receptionof the wireless communication device.

In a fifth aspect, a computer program is provided comprisingcomputer-executable instructions for causing a wireless communicationdevice to perform steps of the method of the third aspect when thecomputer-executable instructions are executed on a processing circuitincluded in the wireless communication device.

In a sixth aspect, a computer program product is provided comprising acomputer readable medium, the computer readable medium having thecomputer program according to the fifth aspect embodied thereon.

In a seventh aspect, a computer program is provided comprisingcomputer-executable instructions for causing an RBS to perform steps ofthe method of the first aspect when the computer-executable instructionsare executed on a processing circuit included in the RBS.

In an eighth aspect, a computer program product is provided comprising acomputer readable medium, the computer readable medium having thecomputer program according to the seventh aspect embodied thereon.

Generally, all terms used are to be interpreted according to theirordinary meaning in the technical field, unless explicitly definedotherwise herein. All references to “a/an/the element, apparatus,component, means, step, etc.” are to be interpreted openly as referringto at least one instance of the element, apparatus, component, means,step, etc., unless explicitly stated otherwise. The steps of any methoddisclosed herein do not have to be performed in the exact orderdisclosed, unless explicitly stated.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure is now described, by way of example, with reference tothe accompanying drawings, in which:

FIG. 1 illustrates a flowchart of a proposed signalling method tosupport uplink short TTI transmissions according to an embodiment;

FIG. 2 illustrates an exemplifying embodiment of a 2-symbol DL sTTIconfiguration in a subframe;

FIG. 3 illustrates an exemplifying embodiment of the mapping between thebit field of a fast UL DCI sent from a DL sTTI and the configuration ofthe scheduled sPUSCH. Only sTTI lengths of 2, 3 and 7 symbols aresupported for sPUSCH;

FIG. 4 illustrates an exemplifying embodiment of signalling eight2-symbol sTTI configurations in a subframe with DMRSmultiplexing/sharing, based on the UL fast DCI bit field mapping shownin FIG. 3 ;

FIG. 5 illustrates an exemplifying embodiment of signaling six2/3-symbol uplink sTTI configurations in a subframe without DMRSmultiplexing/sharing, based on the UL fast DCI bit field mapping shownin FIG. 3 ;

FIG. 6 illustrates an exemplifying embodiment of signaling six2/3-symbol uplink sTTI configurations in a subframe with DMRS sharing,based on the UL fast DCI bit field mapping shown in FIG. 3 ;

FIG. 7 illustrates an exemplifying embodiment of signaling 7-symboluplink sTTI transmissions in a subframe, based on the UL fast DCI bitfield mapping shown in FIG. 3 ;

FIG. 8 illustrates an exemplifying embodiment of the mapping between thebit field of a fast UL DCI send from a DL sTTI and the configuration ofthe scheduled sPUSCH. sTTI lengths of 2, 4, and 7 symbols are supportedfor uplink sTTI transmissions;

FIG. 9 illustrates an exemplifying embodiment of signaling eight2-symbol uplink sTTI configurations in a subframe with DMRSmultiplexing/sharing, based on the UL fast DCI bit field mapping shownin FIG. 8 ;

FIG. 10 illustrates an exemplifying embodiment of signaling six2/3-symbol sTTI configurations in a subframe without DMRSmultiplexing/sharing, based on the UL fast DCI bit field mapping shownin FIG. 8 ;

FIG. 11 illustrates an exemplifying embodiment of signaling six2/3-symbol uplink sTTI configurations in a subframe with DMRS sharing,based on the UL fast DCI bit field mapping shown in FIG. 8 ;

FIG. 12 illustrates an exemplifying embodiment of signaling 7-symboluplink sTTI in a subframe, based on the UL fast DCI bit field mappingshown in FIG. 8 ;

FIG. 13 illustrates an exemplifying embodiment of signaling 4-symboluplink sTTI in a subframe, based on the UL fast DCI bit field mappingshown in FIG. 8 ;

FIG. 14 illustrates an exemplifying embodiment of the mapping betweenthe bit field of a fast DL DCI send from a DL sTTI and the configurationof the scheduled sPUCCH. sTTI lengths of 2, 4, and 7 symbols aresupported for uplink sPUCCH transmissions;

FIG. 15 illustrates an exemplifying embodiment of signaling usage of 2,3, 4, and 7-symbols sPUCCH sTTI in a subframe, based on the DL fast DCIbit field mapping shown in FIG. 14 ;

FIG. 16 a illustrates a wireless communication device according to anembodiment; and

FIG. 16 b illustrates an RBS according to an embodiment.

DETAILED DESCRIPTION

Embodiments will now be described more fully hereinafter with referenceto the accompanying drawings, in which certain embodiments are shown.Embodiments in many different forms are envisaged and should not beconstrued as limited to the embodiments set forth herein; rather, theseembodiments are provided by way of example so that this disclosure willbe thorough and complete, and will fully convey the scope to thoseskilled in the art. Like numbers refer to like elements throughout thedescription.

As previously has been mentioned, in uplink transmissions, one or moreSC-FDMA symbols with DMRS transmitted for each short TTI leads to anincreased overhead and a corresponding decrease in data rates, when thelength of the TTI is reduced.

To reduce the overhead, the reference signals from several transmittersmay be multiplexed into the same SC-FDMA symbol while the user data fromdifferent transmitters are transmitted in separate SC-FDMA symbols.

Further, downlink short sPDSCH may not necessarily contain DMRS ifrecent DMRS transmissions to the same UE have occurred. The presence ofDMRS in a downlink short TTI is either signalled in the sPDCCH or the UEattempts to blindly decode the transmission under the two assumptionsthat DMRS is present or not. This dynamic DMRS insertion can be alsoapplied to sPUSCH for uplink transmissions within short TTIs.

Moreover, the DCI for an uplink grant may be divided into two parts,that is, a slow grant and a fast grant. The slow grant containsfrequency resource allocation information. This grant is transmitted onSF basis in downlink, and it is common for a group of users. The fastgrant is user specific, and it is transmitted on symbol basis indownlink. Dynamic configuration of the short TTI duration for an uplinktransmission is performed based on the information conveyed in the fastgrant.

A signalling method is proposed to support uplink short TTItransmissions according to an embodiment. This method will be describedin the following with reference to the flowchart of FIG. 1 , where RBS102 denotes a Radio Base Station while WCD 103 denotes a wirelesscommunication device,

General Signalling Procedure

Radio Base Station:

S1. Optionally detects need for data for a wireless communication device103, e.g. the Radio Base Station 102 detects that there is a need forthe wireless communication device 103 to receive data in the downlink,or transmit data in the uplink, for instance by receiving data intendedfor the wireless communication device 103 or by receiving a transmissionrequest from the wireless communication device 103,

S2. Optionally decides upon time and amount of resources forcommunication with the wireless communication device 103 including DMRS(Demodulation Reference Signal),

S3. Optionally selects time interval for transmitting downlink controlchannel, e.g. a particular downlink sTTI index is selected where DCI istransmitted,

S4. Determines bit fields in DCI (Downlink Control Information, e.g. afast DCI),

S5. Transmits downlink control channel containing DCI (e.g. a fast DCI),e.g. the Radio Base Station 102 indicates and/or issues a grant for thewireless communication device 103 to transmit or receive data based onDCI and a position of the DCI within a data frame of the downlinkcontrol channel, and

S8. Optionally, transmit (or receive) data to (or from) wirelesscommunication device 103 in accordance with the indicated and/or issuedgrant.

Wireless Communication Device:

S6. Receive and decode downlink control channel, e.g. decode receivedDCI,

S7. Determine configuration including DMRS for communication based onDCI and position of decoded control channel, and

S8. Optionally, transmit (or receive) data to (or from) RBS 102 based onthe indicated and/or issued grant.

Hence, the bit fields of the DCI and the position of the DCI indicatesthe particular TTI configuration to be complied with for the datatransmission/reception stipulated by the indicated and/or issued grant.

Mapping of the Bit Field in a DCI to the Configuration for Transmissions

In an embodiment, the mapping of the field in a DCI to the configurationfor a transmission is defined based on a latency optimized approach,such that the time duration between a received DCI and the correspondingtransmission is as short as possible. This approach may result in a needfor supporting more DCI configurations in some DL TTIs as compared tothe other DL TTIs. Here, a lower limit of this time duration may dependon processing capacity in the UE.

In another embodiment, the mapping of the field in a DCI to theconfiguration for a transmission is defined based on a load balancedapproach, such that the number of supported configurations for atransmission is equally distributed among different DL TTIs, and thenumber of bits required for the signalling is minimized.

In one embodiment, shorter TTIs have a shorter uplink scheduling timing(time between a received DCI and the corresponding uplink transmission)as compared to longer sTTIs. For example, a 2/3-symbol sTTI has ashorter uplink scheduling timing as compared to 7-symbol sTTI. In oneembodiment, sTTIs with a reference signal in the first OFDM/SC-FDMAsymbol have a shorter uplink scheduling timing (time between a receivedDCI and the corresponding uplink transmission) as compared to sTTIs withthe same length, but with user data in the first OFDM symbol of thesTTI. For example, a 3-symbol sTTI configured with DMRS transmitted inthe first symbol, and data transmitted in second and third symbols ofthe sTTI has a shorter uplink scheduling timing as compared to a3-symbol sTTI configured with DMRS transmitted in the last symbol, anddata transmitted in the first two-symbols of the sTTI.

As is understood, downlink (DL) transmissions are performed by a RadioBase Station (RBS) to a wireless communication device, such as a smartphone, a tablet, a smart watch, a gaming console, a television set, etc.This is commonly referred as a User Equipment. In LTE, the RBS isreferred to as an evolved NodeB (eNodeB) and for 5G gNodeB. Accordingly,uplink (UL) transmissions are performed by the wireless communicationdevice to the RBS.

In an embodiment, an uplink data resource is scheduled by an UL fastDCI, which is transmitted on symbol basis (or on every second or moresymbol) in a DL short TTI. A field in the UL fast DCI together with theindex of the DL sTTI where the UL fast DCI is transmitted indicate theconfiguration of the scheduled uplink sTTI transmission, including theDMRS configuration, the data symbol configuration, and the short TTIlength.

In an embodiment, a resource for uplink control channel transmission isscheduled by a DL fast DCI, which is transmitted on symbol basis (or onevery second or more symbol) in DL. A field in the DCI, such as a DLfast DCI, together with the position where the DCI, such as a DL fastDCI, is transmitted to indicate the configuration of the scheduleduplink control channel transmission, including the DMRS configuration,the data symbol configuration, and/or the TTI length.

In the following, exemplifying embodiment are described on how to signalgrants for uplink data channel transmissions and uplink control channeltransmissions with shortened TTI lengths.

Mapping of the Bit Field in a DCI to the Configuration for Uplink DataChannel Transmissions

In an embodiment, the mapping of the uplink sTTI configurations and thefield signalled in an UL fast DCI is defined based on an approach foroptimizing latency, such that the time duration between a receiveduplink DCI in a DL sTTI and the uplink transmitting in an UL sTTI is asshort as possible. The time duration depends on processing capacity inthe UE.

In another embodiment, the mapping of the uplink sTTI configurations andthe field signalled in an UL fast DCI is defined based on the loadbalancing approach, such that the number of UL sTTI configurations isequally distributed among different DL sTTIs, and the number of bitsrequired for the signalling is reduced.

For the case where the number of DL sTTIs and the number of UL sTTIs arethe same within a subframe, the mapping solutions based on the optimizedlatency approach and the load balancing approach are the same. That isthe mapping of the uplink sTTI configurations and the field signalled inan UL fast DCI is defined based on a fixed one-to-one mapping betweenthe DL sTTI and the UL sTTI.

In one embodiment, shorter TTIs have a shorter time between grant andtransmission as compared to longer TTIs.

In a further embodiment, TTIs with a reference signal in the first OFDMsymbol have a shorter time between grant and transmission as compared toTTIs with the same length, but with user data in the first OFDM symbolof the TTI.

In the following, some exemplifying embodiments are given on how toconfigure the bit field mapping based on a load balanced approach.

These exemplifying embodiments are based on the following assumptions:

1. The 2/3-os DL short TTI pattern is shown in FIG. 2 , where the firstthree OFDM symbols are used for PDCCH (“os” denoting OFDM symbols).

2. The minimum UL scheduling timing with UL grant in sTTI number N forsPUSCH transmissions is

-   -   N+6 TTIs timing for an uplink short TTI of 20S, allowing for at        least 9 to 10 os processing (5 short TTI) between last os of        grant and first os of UL transmission    -   N+5 TTIs timing for an uplink short TTI of 4os, allowing for        16os processing (4 short TTI) between last os of grant and first        os of UL transmission    -   N+4 TTIs timing for an uplink short TTI of 7os, allowing for        21os processing (3 short TTI) between last os of grant and first        os of UL transmission.

Thus, FIG. 2 shows a subframe where the particular TTI configuration tobe complied with for the data transmission/reception of a wirelesscommunication device as stipulated by the grant indicated and/or issuedby a Radio Base Station is indicated by the bit fields of the DCI andthe position of the DCI, e.g. the DL sTTI index.

Dynamic Signalling of Uplink sTTI Data Channel Transmissions of Length2, 3 and 7 SC-FDMA Symbols

A field of 2 bits in the UL fast DCI together with the DL sTTI index canbe used for indicating different uplink short TTI configurations. Anexemplifying embodiment of the bit field mapping is shown in FIG. 3 . Inthis example, the first DL sTTI is not used for sending UL fast DCI.

As can be seen in FIG. 3 , e.g. in the top left illustration, the actualposition of the DCI within the subframe of the downlink in combinationwith a value of the DCI determines whether a grant will be indicatedand/or issued to the wireless communication device to transmit UL dataor receive DL data.

As can be seen, DL sTTI1 denotes a particular position of the DCI withinthe DL subframe, while the value of the DCI—i.e. the value expressed inthe DCI bit field—denotes a particular configuration. In this particularembodiment, 4 different configurations (0-3) are possible.

Hence, a particular position (e.g. a particular DL sTTI index) of theDCI within the DL subframe in combination with a particular DCI valuewill represent a particular configuration. It may for instance beenvisaged that a DCI having a value of “2” being transmitted with DLsTTI index=“3” will represent an indicated and/or issued grant for thewireless communication device to transmit or receive data. In thisparticular example, DCI having a value of “2” being transmitted with DLsTTI index=“3” indicates uplink transmission of a DMRS at UL sTTIindex=₇ and of data at UL sTTI index=8.

Throughout the figures, an uplink symbol indicated with “R” carries DMRSwhile blank symbols carry data.

As can be seen in FIG. 3 , different sTTI lengths may also be indicatedwith DCI and its position. The previous example of DCI having a value of“2” being transmitted with DL sTTI index=“3” indicates an sTTI length oftwo symbols, while DCI having a value of “3” being transmitted with DLsTTI index=“3” indicates an sTTI length of seven symbols.

Hence, in an embodiment the DCI and the position of the DCI within adata frame of a downlink control channel indicates the DMRSconfiguration, the data symbol configuration, and the sTTI length of acorresponding data frame for uplink transmission of the wirelesscommunication device.

FIG. 4 illustrates an exemplifying embodiment of configuring eight2-symbol uplink short TTI transmissions within a subframe, by using theUL fast DCI bit field mapping shown in FIG. 3 . The arrows in FIG. 4indicate the UL scheduling timings for different sPUSCH transmissions.The number(s) in the boxes below each DL sTTI is the value of the bitfield used in the UL fast DCI(s) transmitted from this DL sTTI forsignaling a sPUSCH transmission.

For example, two UL fast DCIs are transmitted from “DL sTTI index 1”with the bit field values set to 0 and 1, respectively. Then, based onthe bit field mapping rule shown in FIG. 3 , these two UL fast DCI willsignal two uplink sTTI transmissions, e.g., UL sTTI 0 and UL sTTI 1 inFIG. 4 . In FIG. 4 a), an UL fast DCI with the bit field value of 1 istransmitted from DL sTTI index 2, therefore, an uplink sTTI transmissionis scheduled with configuration of transmitting DMRS at symbol index 5and data at symbol index 6, i.e. “UL sTTI 2” shown in FIG. 4 a). It isalso possible to support DMRS sharing between “UL sTTI 2” and “UL sTTI3” as shown in FIG. 4 b), where the DMRS transmitted in “UL sTTI 2” isused for the channel estimate for the data transmitted in “UL sTTI 3”.Thus, symbol 5 in “UL sTTI 3” is used for data transmission instead ofDMRS. This DMRS sharing is enabled by transmitting an UL fast DCI withthe bit field value of 1 from “DL sTTI index 3”.

Different uplink short TTI transmissions can be dynamically configuredby using a different combination of the UL fast DCIs transmitted fromdifferent DL sTTIs. FIG. 5 illustrates an exemplifying embodiment ofconfiguring six 2 and 3 symbols uplink short TTI transmissions within asubframe without DMRS multiplexing or sharing. It is also possible tosupport DMRS sharing of consecutive sTTIs as shown in FIG. 6 , where theDMRS is not transmitted in the second sTTI or the third sTTI of eachslot.

FIG. 7 illustrates an exemplifying embodiment of signalling two 7ossPUSCH transmissions within a subframe, by using the UL fast DCI mappingshown in FIG. 3 .

For 2 symbols sTTIs, all or some UL DCI in one subframe are indicatingUL grants in the subsequent sub-frame. Thus, no UL DCI is used for an ULgrant in the same sub-frame. For 7 symbols sTTIs, the UL DCI in onesub-frame is always indicating an UL grant in the next-next sub-frame.

Dynamic Signalling of Uplink sTTI Data Channel Transmissions of Length2, 3, 4 and 7 SC-FDMA Symbols

If more UL sTTI configurations need to be supported, e.g. support ofsTTI length of 4 symbols or support of other DMRS configurations of2-symbol sTTI, then, either more bits need to be added in the field inthe UL fast DCI, as compared to the 2 bits as described previously, orthe first DL sTTI, which contains the PDCCH, need to be used fortransmitting UL fast DCI

In the following, exemplifying embodiments will be described on how toundertake signalling of uplink sTTI transmissions, when sTTI lengths of2, 3, 4, and 7 symbols are supported.

Similar to previous embodiments, a field of 2 bits in the UL fast DCItogether with the DL sTTI index can be used for indicating differentuplink sTTI configurations. An exemplifying embodiment of the bit fieldmapping is shown in FIG. 8 . Note that in this exemplifying embodiment,the first DL sTTI (which is allocated to PDCCH) is used for sending ULfast DCI.

In FIG. 9 to FIG. 13 illustrations are given of exemplifying embodimentsof dynamically configuring uplink sTTI transmissions within a subframefor different sTTI lengths, by using the UL fast DCI bit field mappingshown in FIG. 8 .

For 2 symbols sTTIs, most UL DCI in one subframe are indicating ULgrants in the subsequent sub-frame. However, the DL DCI transmittedwithin the PDCCH might be used for UL grants within the same sub-frame,see illustration in FIG. 9 . An alternative mapping might be definedsuch that all DL DCI indicate UL grants in the sub-frame after thesub-frame with the UL DCI.

For 7 symbols sTTIs, the UL DCI in one sub-frame is always indicating anUL grant in the next-next sub-frame per FIG. 12 .

For 4 symbols sTTIs, the UL DCI in one sub-frame is always indicating anUL grant in the next sub-frame per FIG. 13 .

Dynamic Signalling of Uplink sTTI Control Channel Transmissions

Previously, it has been discussed how to dynamically signal uplink datachannel configurations in short TTIs. In the following, exemplifyingembodiments will be described on how to dynamically signal short uplinkcontrol channel (sPUCCH) configurations in short TTIs. Since HARQ for DLdata is transmitted in the uplink control channel, the indication ofsuch channel should be in the fast DL DCI.

By defining 2 bits in the fast DL DCI, the UE can be instructed to sendthe DCI on 4 different sPUCCH options per DL sTTI location, similar tothe fast UL DCI for sPUSCH, see example in FIG. 14 . This way, up to 4different sPUCCH patterns are supported for the DL sTTI pattern. Anexample of this is shown in FIG. 15 , where the sPUCCH TTI signalled inthe fast DL DCI are combined into 4 different sPUCCH patterns.

The above exemplifying embodiments can be modified by also including afast DL DCI with sPUCCH configuration index for 14-symbol (legacy)length, for instance by removing the 4-symbol configurations. This canbe used to ensure good coverage of the sPUCCH.

In an embodiment, a downlink transmission is scheduled by a DL fast DCI,which is transmitted on symbol basis (or on every second or more symbol)in DL. A field in the DL fast DCI together with the position where theDL fast DCI is transmitted indicate the configuration of the scheduleddownlink transmission, including the DMRS configuration, the data symbolconfiguration, and/or the TTI length.

The same methodology proposed for mapping the field of DCI to theconfiguration of an uplink transmission can be used for DL transmissionsas well.

Slot-Length and TDD Usage

In the case operation with 7-symbol (i.e. slot-length) DL TTI, the ULTTI should also be 7-symbol (slot-length). Therefore, there is no needto indicate a specific sPUSCH or sPUCCH configuration. The 2 bitsdefined in the fast DL and UL DCI to indicate the UL transmissions asdescribed in the previous sections may still be defined also for thefast DCI in the slot-length DL TTI.

In one embodiment, the 2 bits in the DL and UL DCI are used to indicatea legacy length (14-symbol) TTI in UL for sPUSCH and sPUCCH, when the DLsTTI length is 7 symbols.

In yet another embodiment, when the DL TTI length is 7-symbols(slot-length), different configurations for the 14-symbol UL TTI issignaled using the 2 bits in fast DL and UL DCI. These configurationscan be e.g. n+2 or n+3 timing as compared to n+₄ timing. As one example,a first index is used to indicate slot-length UL, a second index tosignal 14-symbol UL with n+₄ timing, a third index to signal 14-symbolUL with n+₃ timing, and a fourth index to signal 14-symbol UL with n+2timing.

However, in TDD with slot-length operation in UL and DL, there may be aneed to indicate which in a set of future UL TTI is scheduled with thefast UL DCI. In one embodiment, the 2 bits in the fast UL DCI defined inthe sections above are reused for this purpose. In another embodiment,the 2 bits in the fast DL DCI are reused for transmitting the DownlinkAssignment Index (DAI).

FIG. 16 a illustrates a wireless communication device 103 (referred toas a UE in the following) according to an embodiment, while FIG. 161Dillustrates an RBS 102 according to an embodiment.

Actions performed by the UE 103 according to embodiments may beperformed by a processing circuit 121 embodied in the form of one ormore microprocessors arranged to execute a computer program 122downloaded to the storage medium 123 associated with the microprocessor,such as a Random Access Memory (RAM), a Flash memory or a hard diskdrive.

The processing circuit 121 is arranged to cause the wirelesscommunication device 103 to carry out actions according to embodimentswhen the appropriate computer program 122 comprising computer-executableinstructions is downloaded to the storage medium 123 and executed by theprocessing circuit 121. The storage medium 123 may also be a computerprogram product comprising the computer program 122. Alternatively, thecomputer program 122 may be transferred to the storage medium 123 bymeans of a suitable computer program product, such as a DigitalVersatile Disc (DVD) or a memory stick. As a further alternative, thecomputer program 122 may be downloaded to the storage medium 123 over anetwork. The processing circuit 121 may alternatively be embodied in theform of a digital signal processor (DSP), an application specificintegrated circuit (ASIC), a field-programmable gate array (FPGA), acomplex programmable logic device (CPLD), etc.

Actions performed by RBS 102 of FIG. 16 b according to embodiments maybe performed by a processing circuit 131 embodied in the form of one ormore microprocessors arranged to execute a computer program 132downloaded to the storage medium 133 associated with the microprocessor,such as a Random Access Memory (RAM), a Flash memory or a hard diskdrive. The processing circuit 131 is arranged to cause the RBS 102 tocarry out actions according to embodiments when the appropriate computerprogram 132 comprising computer-executable instructions is downloaded tothe storage medium 133 and executed by the processing circuit 131. Thestorage medium 133 may also be a computer program product comprising thecomputer program 132. Alternatively, the computer program 132 may betransferred to the storage medium 133 by means of a suitable computerprogram product, such as a Digital Versatile Disc (DVD) or a memorystick. As a further alternative, the computer program 132 may bedownloaded to the storage medium 133 over a network. The processingcircuit 131 may alternatively be embodied in the form of a digitalsignal processor (DSP), an application specific integrated circuit(ASIC), a field-programmable gate array (FPGA), a complex programmablelogic device (CPLD), etc.

In an embodiment, an RBS configured to schedule resources for a wirelesscommunication device is provided. The RBS is further configured toindicate and/or issued a granted resource for the wireless communicationdevice to transmit or received data based on Downlink ControlInformation (DCI) and a position of the DCI within a data frame of adownlink control channel.

The RBS thus comprises means for indicating and/or issuing a grant forthe wireless communication device to transmit or received data based onDownlink Control Information (DCI) and a position of the DCI within adata frame of a downlink control channel.

In an embodiment, the RBS comprises a processing circuit and a memory,the memory containing instructions executable by the processing circuit,whereby the RBS is operative to indicate and/or issue a granted resourcefor the wireless communication device to transmit or received data basedon Downlink Control Information (DCI) and a position of the DCI within adata frame of a downlink control channel.

In a further embodiment, a wireless communication device is provided.The wireless communication device is configured to receive a data frameof a downlink control channel from an RBS, and determine a grantedresource of transmission or reception of data is indicated and/or issuedbased on Downlink Control Information (DCI) and a position of the DCIwithin a data frame of a downlink control channel.

The wireless communication device thus comprises means for receiving adata frame of a downlink control channel from an RBS, and means fordetermining whether a granted resource of transmission or reception ofdata is indicated and/or issued based on Downlink Control Information(DCI) and a position of the DCI within a data frame of a downlinkcontrol channel.

In a further embodiment, the wireless communication device comprises aprocessing circuit and a memory, the memory containing instructionsexecutable by the processing circuit, whereby the wireless communicationdevice is operative to receive a data frame of a downlink controlchannel from an RBS, and to determine whether a granted resource oftransmission or reception of data is indicated and/or issued based onDownlink Control Information (DCI) and a position of the DCI within adata frame of a downlink control channel.

The disclosure has mainly been described above with reference to a fewembodiments. However, as is readily appreciated by a person skilled inthe art, other embodiments than the ones disclosed above are equallypossible within the scope of the disclosure, as defined by the appendedpatent claims.

The invention claimed is:
 1. A method performed at a wirelesscommunication device of being granted one of data transmission and datareception, the method comprising: receiving a downlink control channelcarrying downlink control information, DCI, from a Radio Base Station,RBS; and determining a granted resource of transmission or reception ofdata based on DCI and a time position of the DCI within a sub frame ofthe downlink control channel.
 2. A wireless communication deviceconfigured to determine whether one of data transmission and datareception is granted, the wireless communication device comprising aprocessing circuit and a memory, the memory containing instructionsexecutable by the processing circuit to configure the wirelesscommunication device to: receive a downlink control channel carryingdownlink control information, DCI, from a Radio Base Station, RBS; anddetermine a granted resource of transmission or reception of data basedon a bit field of DCI and a time position of the DCI within a subframeof the downlink control channel.
 3. A method performed at a wirelesscommunication device of being granted one of data transmission and datareception, the method comprising: receiving a downlink control channelcarrying downlink control information, DCI, from a Radio Base Station,RBS; determining a granted resource of transmission or reception of databased on a bit field of DCI and a time position of the DCI within asubframe of the downlink control channel; and determining DemodulationReference Signal, DMRS, configuration for one of uplink transmission anddownlink reception from the DCI and the time position of the DCI withinthe subframe of the downlink control channel.
 4. The method of claim 3,further comprising: one of transmitting data to, and receiving datafrom, the RBS using the granted resource.
 5. The method of claim 3,further comprising: determining, from the DCI, a position of a DMRS tobe transmitted at uplink transmission.
 6. The method of claim 3, whereinthe time position of the DCI within the subframe of the downlink controlchannel is given by a downlink short Transmission Time Interval, sTTI,index number at which the DCI is transmitted.
 7. The method of claim 3,further comprising: determining scheduling of a granted uplink resourcefrom a time position of the DCI within the subframe of the downlinkcontrol channel.
 8. The method of claim 3, wherein for the received DCI,the granted resource is scheduled for uplink transmission at apredetermined number of short Transmission Time Intervals, sTTIs, fromthe sTTI in which the DCI is received.
 9. A method performed at awireless communication device of being granted one of data transmissionand data reception, the method comprising: receiving a downlink controlchannel carrying downlink control information, DCI, from a Radio BaseStation, RBS; determining a granted resource of transmission orreception of data based on a bit field of DCI and a time position of theDCI within a subframe of the downlink control channel; and determiningshort Transmission Time Interval, sTTI, length of a correspondingsubframe for one of uplink transmission and downlink reception from theDCI and the time position of the DCI within the subframe of the downlinkcontrol channel.
 10. The method of claim 9, further comprising: one oftransmitting data to, and receiving data from, the RBS using the grantedresource.
 11. The method of claim 9, further comprising: determining,from the DCI, a position of a Demodulation Reference Signal, DMRS, to betransmitted at uplink transmission.
 12. The method of claim 9, whereinthe time position of the DCI within the subframe of the downlink controlchannel is given by a downlink sTTI index number at which the DCI istransmitted.
 13. The method of claim 9, further comprising: determiningscheduling of a granted uplink resource from a time position of the DCIwithin the subframe of the downlink control channel.
 14. The method ofclaim 9, wherein for the received DCI, the granted resource is scheduledfor uplink transmission at a predetermined number of sTTIs from the sTTIin which the DCI is received.